The Language lexer associations are stored in stylers.xml – this is found in %AppData%\Notepad++\ for normal installations, or in the same directory as notepad++.exe for portable or “local config” versions.

For example, I have the User Ext.: for XML set to include .officeUI files:

    <LexerType name="xml" desc="XML" ext="officeUI">
        <WordsStyle name="XMLSTART" styleID="12" fgColor="FF0000" bgColor="FFFF00" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="XMLEND" styleID="13" fgColor="FF0000" bgColor="FFFF00" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="DEFAULT" styleID="0" fgColor="000000" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
        <WordsStyle name="COMMENT" styleID="9" fgColor="008000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="NUMBER" styleID="5" fgColor="FF0000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="DOUBLESTRING" styleID="6" fgColor="8000FF" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
        <WordsStyle name="SINGLESTRING" styleID="7" fgColor="8000FF" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
        <WordsStyle name="TAG" styleID="1" fgColor="0000FF" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="TAGEND" styleID="11" fgColor="0000FF" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="TAGUNKNOWN" styleID="2" fgColor="0000FF" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="ATTRIBUTE" styleID="3" fgColor="FF0000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="ATTRIBUTEUNKNOWN" styleID="4" fgColor="FF0000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="SGMLDEFAULT" styleID="21" fgColor="000000" bgColor="A6CAF0" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="CDATA" styleID="17" fgColor="FF8000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
        <WordsStyle name="ENTITY" styleID="10" fgColor="000000" bgColor="FEFDE0" fontName="" fontStyle="2" fontSize="" />
    </LexerType>

The critical point is the ext="officeUI" attribute in the opening <LexerType ...> tag.
In my stylers.xml, any language that doesn’t have user-defined extensions will show up with ext="".

You could either copy the whole stylers.xml from your known config, or you could set up some sort of batch/remote to manually edit the ext attribute in the appropriate <LexerType ...> tag(s). (For example, by running sed or equivalent on the remote files.)

I’m not a remote-controlling-other-computers-from-powershell person, but hopefully this will get you moving in the right direction.

Based on your “for example”, you seem to want to associate the “.config” extension with the XML language parser, and associate the “.log” extension with the normaltext language parser.

Settings > Style Configurator

• select XML in the left Language: column.
• Under User Ext.:, add config (no dot)

I don’t think you need to do anything special to associate “.log” with normal text (because any extension that matches nothing will be interpreted as plain text) – unless you have a language parser that already handles “.log”: when you open a filename.log, what shows up in the lower left on the status bar; if it’s “Normal text file”, then it’s already using the non-parser of normal text. If it says “User Defined File – blah”, then look under Language > Define Your Language..., and select the appropriate User Language and check the list of Ext.:. If NPP’s status bar on the lower left says something else, look in the Style Configurator for a language type that matches that name, and see if it associates itself with “.log” in either the Default ext.: or User ext.: